Wednesday, May 21, 2008

Assessing the Accuracy of the Oregon/Kentucky Predictions: The Big Winner was Pollster.com

While there are still votes to be counted in Oregon, it looks like Obama's margin in that state will be 18%, while Clinton won Kentucky by 35%. So, who came closest to getting the margins correct in both states? The figure below plots the predictions from three survey firms that released polls from both states during the last week of the campaign, along with Poblano's predictions based on demographic models and Pollster.com's poll averages.

While each of these organizations underestimated the size of the Obama margin in Oregon, Pollster.com came closest to getting the results correct in both states. The pollster.com averages had Clinton winning by 35% in Kentucky (which she did) and Obama winning by 12% in Oregon. Among the individual pollsters, it appears as though Survey USA came closest on the pair of margins. While American Research Group was closets on Oregon (they predicted a 36% margin for Clinton), they greatly underestimated Obama's margin of victory in Oregon. Survey USA came closest on the Oregon margin and were only off on the Kentucky margin by 4%.

Unlike two weeks ago, when he nailed the NC and IN outcomes, Poblano's model was the farthest off last night. To his credit, Poblano did state that he thought his predictions for Kentucky were likely to be understating Clinton's support. He was right, he missed that margin by 16%. Poblano's model did come much closer on Oregon.

UPDATED: Post was updated at 2pm on May 21st to reflect the fact that Obama's lead in Oregon is now 18%.

Center for Congressional and Presidential Studies

The Center for Congressional and Presidential Studies (CCPS) is located in the nation's capital at American University. CCPS provides an integrated teaching, research, and study program focusing on Congress and the presidency and the interactions of these two basic American institutions.